A listing of acronyms used herein follows the detailed description section below. In current cellular radio environments there may be various user equipments (UEs) that are operating/coexisting in a given cell that have different capabilities. For purposes of the examples herein these different capabilities may be concisely summarized as UEs operating under 3GPP Release 8/9 and those operating under 3GPP Release 10. Release 10 enables UEs to operate simultaneously on multiple cells in what is termed Carrier Aggregation (CA) mode. In carrier aggregation the bandwidth available for use by the wireless network is divided into multiple component carriers; a given Release 10 UE may be operating on one component carrier designated as a primary cell (Pcell) and one or more further component carriers designated as secondary cells (Scells). Other Release 10 UEs may be operating in a non-CA mode and thus on only one carrier/cell. For conciseness, herein these are referred to as non-CA UEs while those UEs for which there are two or more configured and activated component carriers are CA UEs. In this environment the Release 8/9 UEs operate on only one component carrier/cell.
Data transmitted to any of these UEs is over a data radio bearer, termed herein as a data bearer for brevity. Data bearers may or may not have an associated guaranteed bit rate. A data bearer assigned to a given CA UE may be served by any one or more of the CA UE's multiple active cells. In this manner data bearers are associated with a given UE rather than with a given cell; a single data bearer assigned to a given CA UE may carry data to or from that UE on all of that CA UE's active cells or only one or some of them. In general a given UE can have more than one data bearer active at a given time, for example one high priority data bearer for voice communications and another low priority data bearer for social networking data updates.
One cellular access technology by the 3GPP is E-UTRAN, also known as LTE. In LTE the radio access node (traditionally termed a base station) is known as an eNodeB or eNB, and handles scheduling of uplink and downlink (UL and DL) radio resources for the various active UEs under its control. Conventional practice in LTE for allocating available radio resources by the eNodeB scheduler is somewhat simplistic in that it distributes resources for the CA UE's data equally among that CA UE's serving cells, or in some configured proportion. An example of this is shown at FIG. 2, using the example data bearers and associated UEs in Cell-1, Cell-2 and Cell-3 as listed in FIG. 1.
In this example UE2 through UE7 are either legacy (Rel. 8/9) UEs that are not CA compatible and are CA compatible (Rel 10) but are presently operating on only one cell. UE1 is the only CA UE and it is active in Cell-1, Cell-2 and Cell-N, so it can get data on its associated data bearer #1 in any one or more of its three serving cells.
FIG. 2 illustrates one prior art technique in which the data for UE1 is equally distributed across its three cells by the eNodeB scheduler. The data to be scheduled in FIG. 2 for UE1 is denoted as packets #1 through #6. Consider each shaded block in the cell-specific tables of FIG. 2 as one physical resource block (PRB) allocated to the correspondingly shaded UE, where the unshaded PRBs are un-allocated and thus go unused. Cell-2 is relatively heavily loaded due to the data volume demands of UE4 and UE5, while Cell-1 is lightly loaded due to lesser data volumes for UE2 and UE3. In FIG. 2 there are 24 PRBs allocated to UE1 in each of its three cells for the illustrated transmission time interval (TTI). Equally distributing resources being allocated to the CA UE1 across all three of its cells means Cell-2 and to a somewhat lesser extent Cell-N are crowded, as compared to the lightly loaded Cell-1. Cell-2 being most heavily loaded spreads out the scheduling of the CA UE1 data in the time domain (horizontal axis) resulting in this data experiencing higher delay. For UE1, packets #2 and #5 are shown in FIG. 2 as being sent in the resources allocated in Cell-2 and experience a longer delay than the packets #1 and #4 for which resources are allocated in Cell-1, which is sparsely loaded as is evident from the larger number of unallocated PRBs and so remains under-utilized.
Since the data volume to be scheduled in any given cell in a CA system is for multiple UEs of which any number of them may not be active in all cells, in this prior art scheduling technique at any point in time the serving cells would nearly always be differently loaded and utilized. The example of FIG. 2 shows how this could result in sub-optimal scheduling of a CA UE across its multiple cells. This can also adversely impact the CA user's experience of a ‘fatter pipe’ for its data in terms of throughput and delay.
What is needed in the art is a mechanism to better utilize the available network resources when scheduling data across multiple cells when at least one data bearer of a UE is active on one or more of those cells.